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Validation of the new Hipparcos reduction
Context: A new reduction of the astrometric data as produced by theHipparcos mission has been published, claiming accuracies for nearly allstars brighter than magnitude Hp=8 to be better, by up to a factor 4,than in the original catalogue. Aims: The new Hipparcosastrometric catalogue is checked for the quality of the data and theconsistency of the formal errors as well as the possible presence oferror correlations. The differences with the earlier publication areexplained. Methods: The internal errors are followed through thereduction process, and the external errors are investigated on the basisof a comparison with radio observations of a small selection of stars,and the distribution of negative parallaxes. Error correlation levelsare investigated and the reduction by more than a factor 10 as obtainedin the new catalogue is explained. Results: The formal errors onthe parallaxes for the new catalogue are confirmed. The presence of asmall amount of additional noise, though unlikely, cannot be ruled out.Conclusions: The new reduction of the Hipparcos astrometric dataprovides an improvement by a factor 2.2 in the total weight compared tothe catalogue published in 1997, and provides much improved data for awide range of studies on stellar luminosities and local galactickinematics.
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
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